Removal of phenolic substances from petroleum fractions



Patented July 6, 1954 REMOVAL OF PHENIOLIO SUBSTANCES FROM PETROLEUMFRACTIONS William K. T. Gleim, Orland Park, Ill., assignor to UniversalOil Products Company, Chicago, 111., a corporation of Delaware NoDrawing. Application January 2, 1952, Serial No. 264,687

6 Claims.

This invention relates ,to a process for the separation of phenols,including phenol itself, the alkyl phenols and thiophenols frompetroleum fractions as a means of improving the petroleum products foruse in motor fuels, burners, etc. More specifically, the inventionconcerns an extraction procedure more commonly referred to as treatingfor the removal of phenols and/or thiophenols particularly from liquidpetroleum distillate fractions utilizing an extractant or treating agentcomprising an aqueous solution of a Water-soluble alkaline earth metalcarbohydrate complex.

The effect of sulfur-containing compounds and phenols normally presentin petroleum distillates and the conversion products of petroleum on thecombustion properties and storage stability of such petroleum-derivedproducts is well known and generally recognized as undesirable. known,for example, that the phenolic and sulfurcontaining compounds present inpetroleum fractions are the major cause of the corrosion of refineryequipment in which the petroleum distillatcs are processed; they aregenerally of disagreeable odor and. their presence in the gasolineproduced therefrom causes undesirable gum formation in internalcombustion engines and reduces substantially the susceptibility of suchgasoline products to the addition of tetraethyl lead anti-knock agentthereto. In the case of fuel oil and diesel fuel distillates ofpetroleum, the phenolic and sulfur-containing components, generallypresent in such distillates, if not previously removed therefrom arebelieved to be the cause of the formation of gum precipitates whichsubsequently clog fuel lines and burner tips in which the fuels arecarried or consumed. Thus, it be,- comes a matter of considerableimportance in the preparation of fuels and other hydrocarbonpetroleum-derived fractions for domestic and commercial use that suchphenolic and sulfur-containing contaminants be removed therefrom priorto their use, and preferably by suitable treatment at the refinery. V

In response to the long recognized need for such refined petroleumproducts, a large number of processes have been proposed to accomplishthe desulfurization and removal of phenolic coma pounds from petroleumproducts, these processes, in general, depending for their efiectivenesson the well recognized acidic nature of the sulfurcontaining andphenolic compounds. The processes heretofore developed for the abovepurposes generally depend upon an extraction or washing procedureutilizing a hydrocarbon-immiscible sol- It is vent which in itself isalkaline or which contains dissolved therein an alkaline substance whichis relatively basic in comparison with such acidic sulfur-containing andphenolic contaminants. Thus, aqueous alkali metal hydroxides such as anaqueous caustic solution, have been found to be effective for thispurpose, not only for treating liquid petroleum distillates, but gaseoushydrogen and hydrocarbon fractions as Well. Certain difliculties,however, are encountered in widespread use of such reagents for thetreatment of hydrocarbon fractions on a commercial scale, includingtheir initial relatively high cost and the stability of the resultingcaustic phenolates and the compounds formed by reaction of the caustictreating agent with the acidic sulfur compounds, the latternecessitating the use of additional auxiliary equipment and therelatively large consumption of utilities, such as heating and coolingfacilities, to effect regeneration of the caustic solution beforerecycling the reagent to the treating or extracting stage of the processin the adaptation of the method to commercial refining operations. Afurther difliculty encountered in the use of reagents containing alkalimetal hydroxides is their highly caustic properties which involveshazards to refinery personnel, corrosion of equipment, etc. The presentinvention provides an extractant, solvent, or treating agent for theremoval of phenolic contaminants, including the phenols and thiophenolsfrom hydrocarbon fractions Without the substantial disadvantagesaccompanying the use of strongly caustic treating agents.

In one of its embodiments the present invention concerns a process forseparating phenolic compounds selected from the group consisting ofphenols and thiophenols from a hydrocarbon contaminated with saidphenolic compounds which comprises contacting the contaminatedhydrocarbon with an aqueous solution of an alkaline earth metalcarbohydrate complex, said carbohydrate being selected from the groupconsisting of the monoand disaccharide ketoses and aldoses containingfrom five to six carbon atoms per saccharide unit.

A more specific embodiment of the invention relates to a process forremoving a thiophenol from a normally liquid hydrocarbon fraction whichcomprises mixing said fraction with a saturated aqueous solution ofcalcium glucosate in an extraction zone therefor, separating theresulting aqueous extract phase from the hydrocarbon raffinate phase,contacting said extract with carbon dioxide, separating the resultingliberated thiophenol from the resulting aqueous phase,

mixing the aqueous phase with calcium oxide at reaction conditionssuificient to form calcium glucosate, and recycling the aqueousglucosate solution to said extraction zone.

The present treating process is particularly applicable to the treatmentof normally liquid hydrocarbon fractions such as the normally liquidhydrocarbon distillates of petroleum, including the gasoline, kerosene,diesel oil, gas oil, and fuel oil fractions. Thus, the invention may beutilized for the removal of phenols and thiophenols from gasolines,particularly straight-run gasolines. The process may also be employedfor the removal of thiophenols from benzene and from cleaners naphthaand for the removal of such phenolic contaminants from gas oil as ameans of pretreating the latter prior to subjecting the same tocatalytic cracking. Although primarily useful for treating normallyliquid petroleum fractions contaminated with sulfur-containingcompounds, the present treating agent may also be contacted with suchfractions in their gaseous state or with normally gaseous hydrocarbonfractions containing phenolic contaminants.

The sulfur compounds which are selectively removed by means of thepresent treating process are the generally acidic thiophenols present inthe petroleum fraction, although under modified conditions of operationother mercaptans, may

be removed from liquid hydrocarbon fractions subjected to the presenttreating process.

The treating agent utilized in the present extraction or treatingprocess is herein characterized as an alkaline earth metal complex of amonoor di-saccharide carbohydrate selected from the aldoses and ketosescontaining from five to six carbon atoms per saccharide unit. Typicalcarbohydrates utilizable in the preparation of the alkaline earth metalcomplexes thereof are such mono-saccharides as glucose, mannose,galactose, fructose, xylose, etc. and such disaccharides as sucrose,maltose, lactose, etc., which although all operable in the process, arenot necessarily equivalent in producing treating agents of the samedegree of effectiveness. In general, glucose represents the leastexpensive and the most effective carbohydrate utilizable in thepreparation of the treating agent. For certain types of hydrocarbonmixtures to be treated requiring aqueous treating solutions of specificproperties, a carbohydrate other than glucose may be preferred. Thetreating agent is prepared by reacting an aqueous solution of thecarbohydrate, preferably containing at least up to about 25% of thecarbohydrate dissolved therein with a basic alkaline earth metalcompound, such as the oxide or hydroxide which is preferably suspendedin Water and reacted with the carbohydrate in a ballmill at roomtemperature. After suflicient trituration, the excess of alkaline earthcompound is filtered from the aqueous solution of carbohydrate complex.One of the preferred alkaline earth metal compounds with which thecarbohydrate may be reacted to form the present treating agent is abasic compound of calcium, such as calcium oxide, or calcium hydroxide,although the basic compounds of other members of the alkaline earthmetal group, that is, strontium and barium may be employed for thepreparation of the carbohydrate complex treating agent for specificpurposes. The treating agent is prepared by mixing an aqueous solutionof the desired carbohydrate containing from one to about by weight ofthe carbohydrate dissolved therein with the alkaline earth metal oxideor hydroxide, the latter preferably being in a powdered or finelydivided condition, at temperatures of from about 0 to about 100 (3.,preferablt at room temperature or slightly above. The resulting aqueoussolution of mono-, and/or di-alkaline earth metal complex of thecarbohydrate is filtered to remove unreacted or excess alkaline earthmetal compound when present in the reaction mixture and thereby clarifythe aqueous solution for use as treating agent. The mixing of theaqueous carbohydrate solution with the alkaline earth metal basiccompound may best be efiected in a ballmill at tempera tures not over100 C.

A hydrocarbon fraction containing phenolic compounds as contaminantsthereof may be subjected to the action of the treating agent, usually ata temperature below about 100 C. and under sufiicient pressure tomaintain the hydrocarbons and aqueous treating agent in substantiallyliquid phase. The process may be effected in any suitable manner wherebycontact between the hydrocarbon charging stock with the aqueous treatingagent may be effected and whereby provision is made for separating andrecovering the desired products, usually by a suitable decantetion ofthe aqueous phase from the treated hydrocarbon phase.

The treatment may be effected by either a batch-type operation orcontinuously. In a typical batch-type operation, for xaniple, the

, contacted hydrocarbons and treating agent are introduced into a mixingchamber, the two phases entirely mixed therein and thereafter allowed tosettle in the same or a different chad her. The upper hydrocarbon layerwill contain a lower concentration of phenolic compounds therein,particularly of thiophenols and may be withdrawn to storage or may befurther treated to accomplish removal of additional impuritiestherefrom. The lower layer will comprise an aqueous solution of thealkaline earth metal carbohydrate complex in which the phenoliccontaminant of the initial hydrocarbon feed stock is dissolved.

The treating process may be operated continuously by countercurrentcontact between the hydrocarbon charged stock and the treating agent ina countercurrent extraction zone wherein the two phases are maintainedat the above specified reaction temperatures and at pressure sufficientto maintain substantially liquid phase. The aqueous treating agent beinggenerally the phase of greatest density in the extraction zone ispreferably introduced into the top of the extraction column and allowedto flow downwardly against a rising stream of the hydrocarbon feetstock. The extraction zone may be of any suitable design customarilyemployed for extraction operations, such as a bubble plate column, acolumn packed with contacting materials such as quartz chips, berylsaddles etc. or it may simply comprise a vertical tubular columncontaining an arrangement of baffles Within the column to obtain mixingbetween the hydrocarbon and aqueous phases. The treated hydrocarbonphase removed from the top of the extraction column will contain a lowerpercentage of phenolic contaminants while the aqueous treating agentremoved from the bottom of the column will contain a major proportion ofthe contaminants present in the feed stock dissolved therein. In manyinstances the aqueous extracting agent realso the extractant forrecycling purposes.

moved from a particular operation is not completely saturated withrespect to extracted phenolic contaminants and may be capable of furtheruse as the extracting agent in a subsequent extraction operation, forexample in a column placed in series with the preceding extractioncolumn.

The spent or used extraction agent containing the phenolic contaminantsdissolved therein, whether formed in either batch or continuous types ofoperation may be regenerated for recycling in the process by suitableremoval of the contaminating phenolic substances from the extractingagent, One means for regeneration of the alkaline earth metalcarbohydrate complex solution whereby the phenolic materials recoveredfrom the hydrocarbon feed stock may be recovered if desired, comprisessubjecting the spent treating agent to steam distillation, collectingthe distillate which comprises phenols and thiophenols contained in theinitial hydrocarbon feed stock and extracted therefrom. by the presenttreating agent. Another suitable method for regeneration of the treatingagent comprises carbonating the spent treating-agent, preferably at roomtemperature or below, and preferably at a superatmospheric pressure ofcarbon dioxide. In the latter operation, the aqueous treating agentabsorbs carbon dioxide to form carbonic acid which is relatively moreacidic than the phenolic components dissolved in the treating agent, re-Suiting in the displacement of the phenolic compounds ironi the aqueoussolution and precipitation of the alkaline earth metal carbonate fromthe treating solution. The phenolic compounds thereby released from thetreating agent may be recovered by extraction with a relativelywaterimmiscible solvent for the phenolic compounds, such as liquidbutane, pentane, hexane, and other hydrocarbon solvents, ethers such asdi-ethyl ether, di-propyl ether etc. or other suitable waterimmiscibleextractant for the phenols. A preferred solvent for this purpose is onewhich boils at a temperature either above or below the boiling point ofthe phenolic compounds, such that separation of the solvent from therecovered phenols may be effected by distillation, thereby enablingrecovery not only of the phenolic compounds but The alkaline earth metalcarbonate formed during the treatment of the spent treating agent withcarbon dioxide may be filtered from the aqueous solution.

of regenerated carbohydrate, dried and heated to form the alkaline earthmetal oxide which may again be utilized to form the alkaline earth metalcarbohydrate complex, if desired.

Still another method of regenerating the spent treating agent comprisesadding thereto an acid which is stronger than carbonic acid, such assulfuric acid which releases the phenolic compound from its combinationwith the alkaline earth metal carbohydrate and reacts with the alkalineearth metal to form a salt of the latter with the particular acidutilized to release the phenolic compound from the aqueous treatingsolution. The free phenolic compounds may be separated by extractionfrom the resulting aqueous solution in the manner hereinabove describedto recover the phenolic compounds from the resulting aqueous alkalineearth salt phase. The free carbohydrate dissolved in the aqueoussolution may thereafter be reacted with additional alkaline earth metaloxide or hydroxide to form an aqueous solution of the alkaline earthmetal carbo- 6. hydrate for recycling as the regenerated treating agent.

The present process is further illustrated with respect to certainspecific embodiments thereof in the following examples, which however,are not intended to limit the generally broad scope of the invention instrict accordance therewith.

Example I Mono-calcium glucosate was prepared by triturating one mole ofcalcium oxide with one mole of glucose. ml. of water was added to themixture of glucose and calcium oxide, causing an orange-colored mass todevelop, which solidified on further standing. The solid mass was brokenup into particles and steam thereafter passed over the particles until aclear, viscous liquid was formed. The resulting solution was dilutedwith an additional quantity of water in an amount suflicient to form a10% solution of calcium glucosate which was utilized as the treatingagent for the removal of phenolic compounds from a gasoline fraction, ashereinafter described.

A thermally cracked gasoline fraction containing 0.005% phenol and0.001% thiophenol was washed with 10 volume per cent of the above 10%aqueous solution of mono-calcium glucosate at a temperature of 25 C. byplacing the gasoline fraction and aqueous treating agent in a kettle,

Example II A thermally cracked gasoline fraction containing 0.041 phenoland a second fraction containing 0.056% thiophenol were each separatelytreated with ten volume per cent of 10% calcium glucosate solution at 25C. in the method described in Example I above, Analysis of the recoveredhydrocarbon fractions from the treating operation indicated that thegasoline fraction containing 0.041% phenol after washing with thetreating agent contained 0.017% phenol, representing a removal ofapproximately 59% of the phenol from the initial gasoline fraction. Thegasoline feed stock containing initially 0.056% thiophenol after washingwith the treating agent contained less than 0.001 thiophenol,representing approximately 100% removal of the thiophenol originallycontained in the gasoline feed stock.

Example III A calcium sucrate solution was prepared by grinding one moleof calcium hydroxide with one mole of sucrose in a ballmill withsufiicient water to form a 10 aqueous solution of calcium sucrate whichis utilized as the treating agent in the following example to removephenolic compounds from a thermally cracked gasoline fraction. Tenvolume per cent of the calcium sucrate solution is shaken with thethermally cracked gasoline fraction containing 0.048% phenol and 0.035%thiophenol at a temperature of 25 C. The aqueous layer is allowed toseparate from an upper hydrocarbon layer and the latter recovered bydecantation from the aqueous phase. The washed hydrocarbon fractioncontains 0.005% phenol representing approximately 90% removal of theoriginal phenol content o i 'the cracked gasoline fraction and 0.001%thiophenol, representing approximately 97% removal of the latterthiophenol contaminant of the original gasoline fraction.

I claim as my invention:

1. A process for separating phenolic compounds selected from the groupconsisting of phenols and thiophenols from a hydrocarbon containinatedwith said phenolic compounds which comprises contacting the contaminatedhydrocarbon with an aqueous solution of a Water soluble alkaline earthmetal carbohydrate complex, said carbohydrate being selected from thegroup consisting of the monoand di-saccharide ketoses and aldosescontaining from 5 to 6 carbon atoms per saccharide unit.

2. The process of claim 1 further characterized in that said aqueoussolution contains from about 1 to about 25% by Weight of said alkalineearth metal carbohydrate complex.

3.v The process of claim 1 further characterized in that saidcontaminated hydrocarbon and said aqueous solution are contacted at atemperature of from about 0 to about 100 C. and at a pressure sufiicientto maintain the resulting mixture in substantially liquid phase.

4. The process of claim 1 further characterized in that said alkalineearth metal carbohydrate complex is' calcium mono-glucosate.

5'. The process of claim 1 further characterized in that said alkalineearth metal carbohydrate complex is mono-calcium sucrate.

6. The process of claim 1 further characterized inv that said alkalineearth metal carbohydrate complex is a mono-calcium xylosate.

References Cited in the file of this patent UNITED STATES PATENTS-Number Name Date 1,654,154 Ackerman Dec. 27, 1927 1,654,155 AckermanDec. 27, 1927 1,742,020 Ackerman Dec. 31, 1929 1,742,021 Ackerman Dec.31, 1929

1. A PROCESS FOR SEPARATING PHENOLIC COMPOUNDS SELECTED FROM THE GROUPCONSISTING OF PHENOLS AND THIOPHENOLS FROM A HYDROCARBON CONTAMINATEDWITH SAID PHENOLIC COMPOUNDS WHICH COMPRISES CONTACTING THE CONTAMINATEDHYDROCARBON WITH AN AQUEOUS SOLUTION OF A WATER SOLUBLE ALKALINE EARTHMETAL CARBOHYDRATE COMPLEX, SAID CARBOHYDRATE BEING SELECTED FROM THEGROUP CONSISTING OF THE MONO- AND DI-SACCHARIDE KETOSES AND ALDOSESCONTAINING FROM 5 TO 6 CARBON ATOMS PER SACCHARIDE UNIT.